From 77d96145b163d79186c722a7ffccfff57601157c Mon Sep 17 00:00:00 2001
From: Quentin Carbonneaux
Date: Wed, 28 Feb 2018 16:22:02 -0500
Subject: fix unlikely race

XFlush() can in fact fetch events and add them to Xlib's
internal queue.  It happens very rarely with the current
implementation, but when it does, we are missing a UI
update.
---
 gui.h  |  2 +-
 main.c | 33 +++++++++++++++++++--------------
 win.c  |  1 -
 x11.c  |  4 ++--
 4 files changed, 22 insertions(+), 18 deletions(-)

diff --git a/gui.h b/gui.h
index e6c83da..e0b62d8 100644
--- a/gui.h
+++ b/gui.h
@@ -94,7 +94,6 @@ enum {
 struct gui {
 	int (*init)(void);
 	void (*fini)(void);
-	void (*sync)(void);
 	void (*getfont)(GFont *fret);
 	void (*decorate)(GRect *clip, int dirty, GColor color);
 	void (*drawtext)(GRect *clip, Rune *str, int len,
@@ -102,6 +101,7 @@ struct gui {
 	void (*drawrect)(GRect *clip, int x, int y, int w, int h, GColor c);
 	void (*drawcursor)(GRect *clip, int insert, int x, int y, int w);
 	void (*setpointer)(GPointer pt);
+	int (*sync)(void);
 	int (*textwidth)(Rune *str, int len);
 	int (*nextevent)(GEvent *eret);
 	int hmargin;
diff --git a/main.c b/main.c
index 43e4bf8..d6f2616 100644
--- a/main.c
+++ b/main.c
@@ -18,14 +18,17 @@
 
 W *curwin;
 int scrolling;
-int needsredraw;
 
 enum {
 	RedrawDelay = 16, /* in milliseconds */
 	DoubleClick = 600,
 };
+
+static void redraw();
+
 static struct gui *g;
 static int clicks;
+static int needsredraw;
 
 
 void
@@ -47,19 +50,6 @@ resetclicks()
 	clicks = 0;
 }
 
-static void
-redraw()
-{
-	static W *old;
-
-	assert(needsredraw);
-	if (old != curwin && old)
-		old->dirty = 1;
-	win_redraw_frame(curwin, mode == 'i');
-	old = curwin;
-	needsredraw = 0;
-}
-
 void
 repaint()
 {
@@ -157,6 +147,21 @@ gev(int fd, int flag, void *unused)
 	}
 }
 
+static void
+redraw()
+{
+	static W *old;
+
+	assert(needsredraw);
+	if (old != curwin && old)
+		old->dirty = 1;
+	old = curwin;
+	needsredraw = 0;
+	win_redraw_frame(curwin, mode == 'i');
+	if (g->sync())
+		gev(0, 0, 0);
+}
+
 int
 main(int ac, char *av[])
 {
diff --git a/win.c b/win.c
index eae4b13..a7cc523 100644
--- a/win.c
+++ b/win.c
@@ -294,7 +294,6 @@ win_redraw_frame(W *focus, int insert)
 		g->drawrect(&b, 0, 0, b.w, g->border, GGray);
 		draw(&tag.win, GPaleGreen, focus, insert);
 	}
-	g->sync();
 }
 
 /* win_scroll - Scroll the window by [n] lines.
diff --git a/x11.c b/x11.c
index 39961ee..faff022 100644
--- a/x11.c
+++ b/x11.c
@@ -208,11 +208,11 @@ textwidth(Rune *str, int len)
 	return gi.xOff;
 }
 
-static void
+static int
 sync()
 {
 	XCopyArea(d, pbuf, win, gc, 0, 0, w, h, 0, 0);
-	XFlush(d);
+	return XPending(d); // calls XFlush()
 }
 
 static int
-- 
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